1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
//! Definition of the `PollFn` adapter combinator use {Future, Poll}; /// A future which adapts a function returning `Poll`. /// /// Created by the `poll_fn` function. #[derive(Debug)] #[must_use = "futures do nothing unless polled"] pub struct PollFn<F> { inner: F, } /// Creates a new future wrapping around a function returning `Poll`. /// /// Polling the returned future delegates to the wrapped function. /// /// # Examples /// /// ``` /// use futures::future::poll_fn; /// use futures::{Async, Poll}; /// /// fn read_line() -> Poll<String, std::io::Error> { /// Ok(Async::Ready("Hello, World!".into())) /// } /// /// let read_future = poll_fn(read_line); /// ``` pub fn poll_fn<T, E, F>(f: F) -> PollFn<F> where F: FnMut() -> ::Poll<T, E> { PollFn { inner: f } } impl<T, E, F> Future for PollFn<F> where F: FnMut() -> Poll<T, E> { type Item = T; type Error = E; fn poll(&mut self) -> Poll<T, E> { (self.inner)() } }